A work vehicle, such as a tractor, typically includes two brake pedals, each of which is coupled to a corresponding brake cylinder or service brake for braking an associated wheel of the vehicle. For instance, the work vehicle may include a left brake pedal hydraulically connected to a left service brake for braking the left rear wheel of the vehicle and a right brake pedal hydraulically connected to a right service brake for braking the right rear wheel of the vehicle. In addition to the service brakes, the work vehicle may also include or be associated with additional brakes, such as one or more trailer brakes of a trailer or other unit being hauled by the vehicle.
In most conventional braking systems, the trailer brake(s) is coupled to the same hydraulic circuit as the service brake(s) to allow the trailer brake(s) to be actuated via depression of the brake pedal(s). As such, in instances when an operator depresses one of the brake pedals (e.g., the left brake pedal), the associated service brake (e.g., the left service brake) is actuated in combination with the trailer brake(s). Such simultaneous actuation of the trailer brake(s) with the service brake(s) may be advantageous when the work vehicle is travelling at relatively high speeds (e.g., when traveling along a road). However, when the work vehicle is traveling at relatively low speeds (e.g., when working in a field), it is often desirable to be able to steer the work vehicle by actuating one of the service brakes without actuating the trailer brake(s). Unfortunately, conventional braking systems do not provide for this functionality.
To address this lack of functionality, recent attempts have been made to allow for speed-based control of the trailer brake(s). For instance, international publication WO 2014/096156, entitled “A Brake System for Controlling a Brake of a Unit Hauled by a Vehicle” and assigned to CNH Industrial Italia SPA, discloses a braking system that utilizes an inverse shuttle valve in combination with a solenoid valve to provide speed-dependent control of one or more trailer brake(s). While this braking system represents a significant improvement over conventional systems, a need continues to exist for further refinements and improvements of existing braking systems to provide a cost-effective and efficient solution for providing speed-dependent control of the trailer brake(s) associated with a work vehicle.
Accordingly, an improved system and a related valve assembly for providing speed-dependent control of one or more trailer brakes of a hauled unit of a work vehicle would be welcomed in the technology.